Volunteer firefighters are missing and reported looting is of "significant concern" today after a deadly fire and chemical explosion at a Texas fertilizer plant leveled buildings and prompted widespread evacuations.

The fire and explosion Wednesday night in a small town north of Waco sent at least 180 people to hospitals and authorities fear that five to 15 people could be dead.

"Homes have been destroyed. Part of that community is gone," Waco Police Department Sgt. William Swanton said at a news conference today.

The initial blast at the West Fertilizer Plant in West, Texas, occurred just before 8 p.m., but officials still were struggling to tally the dead and injured early this morning and searching door-to-door amid the rubble for survivors, police said.

Swanton said the five to 15 deaths is a "rough number" and they are unverified. "There are still firefighters missing," Swanton said.

He said an estimated three or four who are missing are volunteer firefighters, "meaning that they probably have a very large contingent of people that are willing to risk their lives for the neighbors and community."

They are the first responders who were battling the fire when the explosion occurred, he said.

A firefighter and law enforcement officer who was previously mentioned as missing has been found, Swanton said. He is in a hospital with "pretty serious injuries," he added.

Swanton said authorities are still in search-and-rescue mode and are not yet in recovery mode.

"I don't have a number of how many they have rescued or how many potential bodies they have found," he said.

Swanton also said that there is a "small amount of looting" that has happened and "that is a significant concern to us."

"The town is secure. There are plenty of law enforcement officials that are stationed around the town," Swanton said. "There is no fire out of control. There is no chemical escape from the fertilizer plant that is out of control."

The Red Cross, mental health agencies and grief counselors are on hand to help the community, in addition to the neighbors who are already assisting each other.

"That is a very tight-knit, very family packed, family-oriented community," Swanton said of the town of about 2,800 people. "They are leaning on each others' shoulders."

West EMS Director Dr. George Smith, himself injured and bloody, said he had not personally seen bodies to confirm deaths, but believed the blast killed at least two emergency responders to a fire at the plant before the initial explosion and a person at a nearby apartment complex that suffered serious damage.

In addition, some responders to the fire were believed unaccounted for after the blast, according to Smith, Swanton and West Mayor Tommy Muska.

As they gained access to the explosion site, officials said they were treating it as a crime scene.

"We are not indicating that it is a crime, but we don't know," Swanton said. "What that means to us is that until we know that it is an industrial accident, we will work it as a crime scene. ATF [the federal Bureau of Alcohol, Tobacco, Firearms and Explosives] is conducting the main investigation."

President Obama, in a statement, extended his condolences to the people of West and thanked first responders.

"A tight-knit community has been shaken, and good, hard-working people have lost their lives," he wrote.

"My administration, through FEMA and other agencies, is in close contact with our state and local partners on the ground to make sure there are no unmet needs as search and rescue and response operations continue."

The disaster even drew condolences from Pope Francis, who tweeted, "Please join me in praying for the victims of the explosion in Texas and their families."

Earlier concerns about the possibility of dangerous ammonia fumes and shifting winds subsided by morning as fires died down, Swanton said before 6 a.m. ET.

"Air quality, at this point, is not an issue," Swanton said. "It is not a concern."

Nevertheless, numerous other concerns remained.

Witnesses reported heavy fire or concussive damage to a middle school, homes and an apartment complex near the plant, as well as to a nursing home, where more than 130 residents were evacuated, Mayor Muska said.

Buildings in a radius of about five blocks around the plant -- including at least 60 more homes -- were heavily damaged by the blast, officials said.

"It was almost tornadic in effect," Swanton said. "It looked like to me one home would be fine and next to it there would be extreme devastation."

State Trooper D.L. Wilson of the Texas Department of Public Safety described the initial fertilizer plant blast as "massive -- just like Iraq, just like the Murray Building in Oklahoma City. The same kind of hydrous [ammonia] exploded, so you can imagine what kind of damage we're looking at."

It was felt 20 to 30 miles away, witnesses said, and near the plant it burned buildings, knocked down people, blew out windows and, according to Wilson, left the damaged apartment complex looking like "just a skeleton standing up."

"It's total chaos," West City Councilwoman Cheryl Marak said soon after the blast, according to ABC News Radio. "There's ambulances and fire trucks and police cars from everywhere."

Marak told ABC News that the explosion killed her pet dog and destroyed her house about 2 1/2 blocks from the plant, as well as houses around it.

"With the explosions, the whole street lifted up," she told ABC News. "It was like a massive bomb went off. It demolished both my houses, my mother's and mine."

"I think everything around us is pretty much just gone," she added, according to ABC News Radio.

Keith Williams, a local resident, said his house also was destroyed.

"All the ceilings are out," Williams said, according to ABC News Radio. "The windows are out. The brick's knocked off the house. My big garage out back is half blowed in."

He also saw "people with all their houses tore up across the street from me, on each side of me."

By 5:45 a.m. ET, hospitals near the blast site reported treating 180 people. At least 16 patients at the hospitals were in critical condition and three in serious condition.

Hillcrest Baptist Medical Center in Waco, Texas, saw more than 100 of the wounded, officials there said. Patients from the blast also were confirmed early Thursday at Providence Healthcare Network in Waco, Parkland Hospital in Dallas, and Scott & White Memorial in Temple, Texas.

The fertilizer plant exploded around 7:50 p.m. local time Wednesday, according to the Texas Department of Public Safety.

Emergency response audio told the story of the chaos among firefighters and others at the scene.

"We need every ambulance we can get this way," one snippet said. "A bomb just went off. It's pretty bad."

"Firefighters down," another said. "There has been an explosion."

"The rest home has been seriously damaged. We have many people down. Please respond."

There were subsequent explosions around 10 p.m., ABC News affiliate WFAA reported. The cause of the explosions was unconfirmed, but a dispatcher was heard warning crews to move away from chemicals in unexploded tanks.

Most fires were contained early this morning, officials said, but they continued to burn.

"It was smoldering still and it still is active," Wilson said around 1 a.m. ET. "You know other ingredients [are] at the facility, so we don't want that to explode again. So right now we can't get firefighters in there. We're worried about people right now, not property.

"We're going to go back in and do another house-to-house search and see if anybody else, victims, are in the houses," Wilson said. "That's going to be going on all night."